Magnetic amplifier



y 1951 P. GACHET ETAL 2,552,952

MAGNETIC AMPLIFIER Filed July 15, l948 FIGJ.

1 I INVENTORS H6 2 PAUL-JOSEPH AUGIER DE MONTGREMIEP PAUL GACHET AGENTPatented May 15, 1951 H. =MAGN'ETIC AMPLIFIER Paul Gache't; fvincennes,and Paul Joseph Augier deMontgremienVanves, France, assigners toYvesgRocard, ParisgFrance Applicationiluly 15, 1948, Serial No. 38,935In France March 12, 1948 -12Claims. 1

Our invention relates to magnetic amplifiers, and more particularly .tomagneticvamplifiers in which two similar transductors are provided; Itis well known in the art that :such transductors when connectedinparallel. teen-alternating current source will supply'equaLoutputcurrents onless they are unbalanced by changing thegsaturations of theirmagnetic structures inopposite senses by means of a directcurrent, thefcontrol current. The. change initherel'ation-of the output currents isa multiple onamplification of the change in control current.

It isan-object'of our. invention to: improve 'the range of such magneticamplifiers.

It is another objectof our invention tozenable such amplifiers to'yie1d;higher outputs.

It is also an object of our invention to render such magnetic amplifiersmore e'flicient.

It is a further object of'our invention to provide magnetic amplifierswhich are compact in construction and allow a considerable-reduction ofmetal weight in 'comparison tovknown amplifiers of similar output.

Other objects and advantageswill be-apparent from a consideration ofthe-specification and claims.

According to our invention, .magneticxamplifiers are improved byproviding the :transductors with additional windings influencing thesaturations of their magnetic materials, .said windings being energizedby currents bearing .certainrelations to the currents flowing in themainwindings of the transductors and serving to 'aid the .unbalancing effectof the control current.

Our invention will bebetter understood-from the following detaileddescription, withreference to the accompanying drawing illustratingbyway of example two embodiments of. the same- In the drawings- Fig. 1is a wiring, diagram otamagnetic amplifier according to ourinvention,.-and

Fig. 2 is a modification of the diagram. shown .in Fig. 1.

Referring now to thedrawings andiflrstto Fig.

1, the amplifier shown in the diagram :comprises the. leads 'joiningthesource I to the winding fi. It will be understood that thealternatingcur- .rent flowing in. the winding 6 depends on the state ofsaturation of the material of the magnetic structure. In the transductorshown in the diagram this saturation is controlled by .a plurality ofwindings in which direct current .flows. All these windings are providedin pairs, one winding of each pair on-each of the outer legs I and 2,respectively, and each two windings belonging to the same pairare-connected in series and are wound in such a manner that anyalternating electrornotive forcesinduced :in them by the alternatingcurrent flowing in winding 6 will-cancel each other. Altogetherthere-arethree pairs of direct current windings inuthe transductor as will bemore'iully described-.hereinafter.

The first pairof direct current windings iland I0 is fed from a directcurrent source II supplying what may be termed the contro current. Thisis a current which can be varied'at will by the operator or may besupplied by some controlling device of a type well known'in the art. Itshould benoted that no alternating current will be sent back into thedirect current source I I because, as mentioned above, the controlwindings?! and Marc wound in such a sense thatany electromotive forcesinduced in them cancel each other. It should also benoted thatthe-windings 9, II! are connected in series with thecorresponding-windings 9', IE of the transductor T2 so-that the samecontrol current controls the saturation of the material in bothtransductors. By means of a suitable arrangement of the windings 9'; Illit is achieved that the saturation of/the material is affected inopposite senses in the two transductors so that according to thedirection of the control current either thezinductance of T1 will beincreasedgand that of Tzdecreased or that of Trdecreased and that of T2increased.

The main winding 6 and the series-connected rectifier a of thetransductor T2 are connected in parallel to the correspondingpartsoftransductor T1.

Each transductor is provided..with.a. second pair of windings I2, I3 andI2, I3',respectively, which will be termed cross-reaction? windings fora .reason to be. explainedv presently.v Rectifiers I4, I4 are connectedacross portions of: the main-windings-fi, 6'. respectively, theconnections beingmade by means ofjsliding .tapxcontacts IE,15;,andthroughcondensers I6, I 6', respectively. Aswill be; seen from.the diagram, the windings I2, I3 of transductor T1are;energizedgfromarectifier I4 of transductor T2, and conversely thewindings I2, l3 of T2 drawn their current from rectifier I4 of T1. Thusthe current flowing in I2, I3 will be in direct proportion to thevoltage at the input of rectifier I4, i. e. to that which ap pearsacross winding 6', whereas the current in I2, I 3 is in directproportion to the voltage across winding 6. It will be thus understoodthat there is a cross-reaction between the two transductors. A decreaseof the inductance of T1 gives an increase of the current in winding 6.the voltage across this winding is equal to the product of the intensityof the current in 6, by the impedance of this winding.

Both terms vary in opposite senses but it can be seen that impedancedecreases faster than corresponding intensity increases.

A decrease in the inductance of T1 gives a decrease in the voltageacross winding 6, i. e. gives a decrease in the current that flows inthe crossreaction windings I2, I3 and in turn gives an increase ofinductance of T2 i. e. reduces the current in 6. Conversely, a decreaseof inductance of T2 will increase that of T1 which in turn will decreasethe inductance of T2 even further. Thus it will be understood that thecross-reaction windings greatly enhance the unbalancing effect of thecontrol current. By feeding the rectifiers I4, I4 in an autotransformerconnection from portions of the main windings ES, 6 through condensersIE, IS, respectively, the range and the efficiency of the device aregreatly improved.

Rectifier 8 supplies to a resistance Il' a direct current i1proportional to the alternating current flowing in winding 6, andsimilarly rectifier 8 feeds a resistance I1 with a direct current 22proportional to the alternating current flowing in winding 6'. I 'l andH are parts of the output circuit of the amplifier and may, forinstance, be exciting windings of a reversible motor which will reverseits sense of rotation according as i1 or 12 is larger.

Each transductor is provided with a third pair of direct currentwindings, viz. I8, IQ for T1 and I8, I9 for T2. These windings areconnected in series With one another and with the resistances H and Hand also with an adjustable resistance 20, which preferably is ratherlarge in comparison to the resistances I1 and I1. Thus the wndings I8,I9, I8, I9 will be flowed through by a current which is directlyproportional to the difierence i1i2 and the intensity of this currentcan be adjusted at will by a suitable adjustment of resistance 20.Bearing in mind that the windings are arranged on their respectivetransductors so as to affect the inductances of the latter on oppositesenses, it will be understood that these windings also serve to enhancethe unbalancing effect of the control current.

H is a resistance which may be provided, if desired, in the connectionbetween windings I9 and I8.

The operation of the amplifier is as follows: As long as no controlcurrent is supplied, equal currents flow in I? and I1 owing to thesymmetry of the transductors T and T2. When a control current in acertain direction is supplied, the

transductors will be unbalanced, the inductance of one transductor, sayT1, being decreased and that of T2 increased, owing to the oppositeeffects of the windings 9, I I] and 9, It on the saturation of themagnetic material. Thus the currents in 6 and 6 will tend to becomedifferent and this effect is greatly enhanced by the cross-reactionbetween the two transductors and the efiect of the difference currentflowing in the windings I8, l9 and I8, I9. Thus a relatively largedirect current will flow in resistance I! and a much smaller one inresistance I'I'. When now the direction of the control current isreversed, the current in resistance I 1' will be much larger than thatin I! and it will be seen that, .for instance, a motor in which I! andI1 are exciting windings may be reversed by a relatively weak controlcurrent. It will also be understood that the current flowing inresistance 2| will reverse its direction whenever the control current isreversed.

The modification of the amplifier shown in Fig. 2 is essentially thesame as that illustrated in Fig. 1 except that the rectifiers 8 and 8'are not directly connected in series with the windings 5 and 6',respectively, but through transformers. As will be seen from thediagram, the primary 22 of a transformer is connected in series towinding 6, and correspondingly primary 22 to winding 6'. The secondarywinding 23 of the transformer has its circuit completed by the rectifier8, and similarly rectifier 8 is connected to the secondary 23' of theother transformer. Resistance 20 of the amplifier according to Fig. lcanbe dispensed with here, any adjustment of the difierence current beingmade possible by providing sliding contacts 24, 24 engagin resistancesI1, I'I', respectively.

The operation of the amplifier shown in Fig. 2 is exactly the same asthat of the amplifier described hereinabove.

It will be appreciated that modifications of the disclosed embodimentsof our invention are possible without departing from the spirit of theinvention or the scope of the appended claims.

What we claim is:

1. A magnetic amplifier which comprises: a first transductor including afirst saturable magnetic core structure having a first A. C. windingwound thereon, a second transductor including a second saturablemagnetic core structure having a second A. C. winding wound thereon, aseries connection comprising said first A. C. winding and a firstimpedance, a series connection comprising said second A. C. windin and asecond impedance, means for connecting said series connections inparallel with a source of alternating current, a first saturationwinding wound on said first core structure, means for applying a directcurrent through said first saturation winding proportional to themagnitude of the voltage across said second A. C. winding, a secondsaturation winding wound on said second core structure, means forapplying a direct current through said second saturation windingproportional to the magnitude of the voltage across said first A. C.winding, a control winding wound on each of said core structures, andmeans for connecting said control windings to a source of variable D. C.control current so that a variation in control current causes anincrease in the magnetic saturation of one core structure and a decreasein the magnetic saturation of the other core structure, all of saidwindings being so wound that substantially no alternating current isinduced by said A. C. windings in the outputs of said control and saidsaturation windings.

2. A magnetic amplifier as in claim 1, and a load controlled by thedifference in current flow-- ing through said first and said secondimpedances, respectively.

3. A magnetic amplifier as in claim 2 wherein said means for applying adirect current through said first saturation winding comprises arectifier connected across at least a portion of said second A. C.Winding, and means connecting the D. C. output of said rectifier to saidfirst saturation winding.

4. A magnetic amplifier as in claim 3 wherein said means for applying adirect current through said second saturation winding comprises a secondrectifier connected across at least a portion of said first A. C.winding, and means connecting the D. C. output of said second rectifierto said second saturation winding.

5. A magnetic amplifier as in claim 4 including a third and a fourthsaturation winding wound on said first and second core structures,respectively, in opposite electrical direction to the control winding onthe same core structure, and means for passing a direct current throughsaid third and said fourth saturation windings proportional to themagnitude of the difference in A. C. current passing through said firstand said second impedanccs, respectively.

6. A magnetic amplifier which comprises: a first transductor including afirst saturable magnetic core structure having a first A. C. windingwound thereon, a second transductor including a second saturablemagnetic core structure having a second A. C. winding wound thereon, aseries connection comprising said first A. C. winding and a firstrectifier, a series connection comprising said second A. C. winding anda second rectifier, means for connecting said series connections inparallel with a source of alternating current, a first saturationwinding wound on said first core structure, means for applying a directcurrent through said first saturation winding proportional to themagnitude of the voltage across said second A. C. winding, a secondsaturation winding wound on said second core structure, means forapplying a direct current through said second saturation windingproportional to the magnitude of the voltage across said first A. C.winding, 2. control winding wound on each of said core structures, meansfor connecting said control windings to a source of variable D. C.control current so that a variation in control current causes anincrease in the magnetic saturation of the other core structure, a firstimpedance connected across the D. C. output of said first rectifier, asecond impedance connected across the D. C. output of said secondrectifier, a third and a fourth saturation winding wound on said firstand second core structures, respectively, in opposite electricaldirection to the control winding on the same core structure, and meansfor passing a current through said third and said fourth saturationwindings proportional to the difference in voltage across saidimpedances, all of said windings being so wound that substantially noalternating current is induced by said A. C. windings in the outputs ofsaid control and said saturation windings.

7. A magnetic amplifier as in claim 6, and a load connected between saidfirst and said second impedances.

8. A magnetic amplifier as in claim 6 Wherein said means for passing acurrent through said third and fourth saturation windings comprisesmeans connecting said third and said fourth saturation windings inseries between said first and said second impedances.

9. A magnetic amplifier as in claim 1 which includes a third and'afourth saturation winding wound on said first and second corestructures, respectively, in opposite electrical direction to thecontrol winding of the same core structure, a first rectifier connectedacross said first impedance, a first resistance connected across the D.C. output terminals of said first rectifier, a second rectifierconnected across said second impedance, a second resistance connectedacross the D. C. output terminals of said second rectifier, and meansfor applying a current through said third and said fourth saturationwindings proportional to the diiference in potential across said firstand said second resistances, respectively.

10. A magnetic amplifier as in claim 9, and a load connected betweensaid first and second resistances.

11. A magnetic amplifier as in claim 10, wherein said means for passinga current through said third and said fourth saturation windingscomprises means connecting said third and said fourth saturationwindings in series between said first and said second resistances.

1'2. A magnetic amplifier as in claim 11 wherein said first and saidsecond impedances comprise transformers each having its input terminalsin series with the respective A. C. winding and having its outputterminals connected across the respective rectifier.

PAUL GACHET. PAUL JOSEPH AUGIER. on

MONTGREMIER.

REFERENCES CITED The following references are of record in the file ofthis patent:

UNITED STATES PATENTS Number Name Date 1,914,220 Sorensen June 13, 19332,247,983 Barth July 1, 1941 2,338,423 Geyger Jan. 4, 1944

